feat(protocols): trusted senders are not filed as spam, when the message proves its sender

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

services/protocols/internal/application/usecase/message_headers.go

@@ -18,6 +18,8 @@ const snippetLength = 200
 type MessageHeaders struct {
 	Subject         string
 	FromDisplayName string
+	// FromAddress is the address in From, lowercased, or empty when it does not parse.
+	FromAddress string
 	MessageID       string
 	Snippet         string
 	HasAttachments  bool
@@ -58,6 +60,7 @@ func ExtractMessageHeaders(payload []byte) MessageHeaders {
 
 	if from := msg.Header.Get("From"); from != "" {
 		if addr, err := mail.ParseAddress(from); err == nil {
+			out.FromAddress = strings.ToLower(addr.Address)
 			out.FromDisplayName = truncateUTF8(decodeHeader(addr.Name), 255)
 		} else {
 			// A From that does not parse still often carries a usable name